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HelpTest Code LAB3524 TSH Reflex to Free T4 Level
Clinical System Name
TSH Reflex to Free T4 Level
Synonyms
TSH Rfl FT4
TSH Fl FT4
TSH Rflx FT4
Sample Requirements
Specimen: Whole blood
Container(s): Gold SST, Red, Gold Microtainer, Dark Green/Sodium Heparin, Lt. Green/Lithium Heparin Microtainer, Lavender/EDTA
Preferred Vol: 2.0 mL
Minimum Vol: 1.0 mL
Processing Instructions
Reject due to:
Spin: Y
Aliquot: Y
Temp: 2-8 C
Storage location: CPA refrigerator, FrigD rack. Serum should be removed from separator for storage.
Note: Minimum volume of 1.0 mL may be shared with TSH, T4, free T3, and free T4.
Off-site collection: Spin blood. Transfer serum to plastic aliquot container. Refrigerate.
Stability
| Specimen Type | Temperature | Time |
|---|---|---|
| gel separator with serum | Refrigerated | 24 h |
| separated serum | Room temp | 2 h |
| Refrigerated | 7 d | |
| Frozen -20 C | 6 m |
Availability
| STAT | Performed | TAT |
|---|---|---|
| N | M-Sa, day shift | 1-3 d |
Performing Laboratory
Seattle Children's Laboratory
Department
Department: Chemistry
Location: Chem West
Phone Number: (206) 987-2617
CPT Codes
84443
Methodology
Method: Chemiluminescent microparticle immunoassay (CMIA) by Abbott Alinity i, third generation
Analytical Volume: 0.300 mL serum
Limitations:
Reference Range
| Age |
TSH (mIU/mL) |
Critical High (mIU/mL) |
|---|---|---|
| 0-<4 d | 0.5 - 18.2 | >38.5 |
| 4 d - <1 mo | 0.5 - 6.54 | >11.9 |
| 1 mo - <2 mo | 0.5 - 6.54 | |
| 2 mo - <19 yr | 0.47 - 4.17 | |
| >19 yr | 0.35 - 4.94 |
TSH transitioned platforms from Ortho Vitros 3600 to Abbott Alinity i on August 8, 2022.
There is a 25% negative bias with the new method.